Photographic materials which have good original reproduction properties, stable pocessing solutions and simple replenishment are some of the requirements to comply with the demand on diversity and complexity of printed matter in the photographic plate making field.
Original documents for a line work camera process, in particular, are made with a paste-up of photoset text, hand written text, illustrations and screened photographs. Hence, the original documents comprise a mixture of images having different densities and line widths, and there is a demand for plate making cameras, photographic materials and methods of image formation which reproduce the original documents faithfully. On the other hand, enlargement (screen enlargement) or reduction (screen reduction) of screened photographs is widely used in plate making for catalogues and posters. In plate making where screen dots are enlarged, the number of lines is reduced, and blurred dot reproduction occurs. With reduction, the number of lines per inch is greater than on the original document and the dots become finer. Hence, there is a demand on a method for forming images which have a wider latitude for maintaining the reproducibility of screen gradation.
To comply with a demand on the wider latitude, it is known that line images or screen dot images having a clear distinction between image parts and non-image parts and having high contrast and high black densities, are obtained by processing lith-type silver halide photosensitive materials comprising silver chlorobromides (in which the silver chloride content is at least 50%) with a hydroquinone developers, in which the effective concentration of sulfite ion is very low (normally less than 0.1 mol/liter). However, with these methods the developer is very unstable with respect to aerial oxidation because of the low sulfite concentration in the developer. Various endeavors and devices were used to maintain stable bath activity, but at the present time, processing is very slow, thereby deteriorating operational efficiency.
Consequently, a demand has arisen on an image forming system, in which the instability of image formation with development methods, such as those mentioned above (lith development systems), is overcome, with which development is carried out with processing solutions which have good storage stability, and with which ultra-high contrast photographic characteristics can be realized. Systems in which ultra-high contrast negative images of gamma exceeding 10 are formed by processing surface latent image type silver halide photographic materials are proposed. According to the system, the silver halide photographic material containing specified acylhydrazine compounds is processed in developers of pH from 11.0 to 12.3 which contain at least 0.15 mol/liter of sulfite preservative and which have good storage stability, as indicated in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781.
The above mentioned image forming systems exhibit excellent performance with respect to sharp screen dot quality, processing stability, speed processability, and original reproduction properties, but further improved systems which are more stable and provide original reproduction properties are desired to satisfy a diversity of printed matter required in recent years.
On the other hand, silver chlorobromide emulsions sensitized by gold or sulfur are used for various reasons in systems containing hydrazine, as disclosed in JP-A-53-20921, JP-A-60-83028. JP-A-60-112034, JP-A-61-249161, JP-A-61-47943, JP-A-62-235947, JP-A-63-103232, JP-A-l-120549 JP-A-2-287532 and JP-A-2-293747. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application". ) However, a problem arises on the photographic material with respect to increase in photographic speed and deteriorate in black spotting, when it is stored for a prolonged time.
Black spotting results from tiny black particles of developed silvers which are produced in non-exposing regions where no image is formed inherently. Black spotting becomes more prevalent if there is a reduction in the amount of sulfite ion which is generally used in the developer as a preservative and if the pH is raised. Black spotting inevitably reduces greatly a commercial value of a product as a material for photographic plate making purposes.
Furthermore, the abovementioned image forming systems have a disadvantage in that the photographic speed, gamma and the maximum density (Dmax) are reduced by lowering the pH of the developer or increasing the bromide ion concentration in the developer, which result from processing of a large amount of film. On the other hand, in cases where the number of films processed is small, if the sulfite concentration which is introduced as a preservative is reduced markedly or if the pH is raised by the ageing and fatigue of the developer, black spotting becomes remarkable. At the same time, there is a further disadvantage in that the maximum density is reduced. Methods in which the extent of developer replenishment is increased are used to overcome these disadvantages. These methods, however, increase the developer cost and create problems with waste liquids for example. Thus, a system in which there is no increase in the rate of replenishment, without suffering from the change in photographic speed, the fall in D.sub.max and the extent of black spotting, is very desirable.
Halogen lamps or Xenon lamps are used as light sources for plate making cameras. Photographic materials are generally subjected to orthochromatic sensitization to obtain a suitable camera speed for these light sources. However, orthochromatically sensitized photographic materials are greatly affected by the chromatic aberration of lenses, and it is clear that this is likely to result in a loss of image quality.
The image systems mentioned above exhibit excellent performance with respect to sharp screen dot quality, processing stability, rapid processability and original reproduction characteristics. But as a result of the diversity of printed material in recent years, a system which has improved original reproduction characteristics is now desirable.
The inclusion of 8-hydroxyquinoline and derivatives thereof in silver halide photographic materials is well known, as disclosed, for example, in U.S. Pat. Nos. 3,193,386 and JP-A-59-42535. However, cases in which hydrazine derivatives are used are unknown.
The use of selenium compounds as chemical sensitizers is already well known. Unstable and/or nonunstable type selenium compounds exist in selenium compounds, and the unstable type selenium compounds are disclosed, for example, in JP-B-44-15748, JP-B-43-13489, JP-A-4-25832, JP-A-4-109240 (The term "JP-B" as used herein signifies an "examined Japanese patent publication".) Examples of unstable type selenium sensitizers include isoselenocyanates (for example, aliphatic isoselenates such as allylisoselenocyanate), selenoureas, selenoketones, selenoamides, selenocarboxylic acids (for example, 2-selenopropionic acid, 2-selenobutyric acid), selenoesters, diacylselenides (for example, bis(3-chloro-2,6-dimethoxybenzoyl)selenide), selenophosphates, phosphineselenides and colloidal metallic selenium.
To those in the industry, the structure of the unstable type selenium compounds as sensitizers for photographic emulsions is of no importance provided that the selenium is unstable. It is generally understood that the organic moiety of the selenium sensitizer molecule has no role other than supporting the selenium in the emulsion in an unstable form.
Non-unstable type selenium compounds are disclosed in JP-B-46-4553, JP-B-52-34492 and JP-B-52-34491, and the compounds disclosed in JP-B-46-4553, JP-B-52-34492 and JP-B-52-34491 can be used as non-unstable type selenium compounds. Examples of non-unstable type selenium compounds include for example, selenous acid, potassium selenocyanide, selenoazoles, quaternary salts of selenoazoles, diarylselenides, diaryldiselenides, dialkylselenides , dialkyldiselenides , 2-selenazolidinedione, 2-selenooxazolidinedione and derivatives of these compounds.
Chemical sensitization using tellurium compounds is disclosed, for example, in Canadian Patent 800,958, British Patents 1,295,462 and 1,396,696, and U.S. Pat. No. 3,531,289. It has been disclosed that this has the effect of increasing the photographic speed of the emulsion. The fact that the chemical sensitization of AgBrCl and AgCl emulsions which was prepared in the presence of organic thioether compounds and rhodium salts was carried out with tellurium compounds is disclosed, particularly in, U.S. Pat. No. 3,531,289.
Furthermore, doping silver halide with tellurium compounds during grain formation is disclosed in U.S. Pat. No. 3,772,031.
Cases in which redox compounds which release a development inhibitor by oxidation are included in systems containing hydrazine compound, are disclosed, for example, in JP-A-61-213847 and JP-A-64-72140.